Touching the Front End

Since I was using a different gauge wire, I checked my result

At the point I left off last time I nearly had the LO complete. Winding a toroid and connecting all the pads was the last step to close that stage out. For this step I opted to go ahead and do the toroids first. I don’t understand why people dislike toroids so much, it really isn’t that hard. This build was a T-37-6 with 21 turns of #28 wire. (The schematic calls for 26, but I didn’t have any. I did the calculation for what the inductance should be and measured my result. They matched.) Every time you go through the center of the toroid, count 1. Easy!

If your wondering about my L/C Meter. They are unfortunately unavailable. Its a really sad story. . .

This is the front end nearing completion

Since I already had the pads laid out for the local oscillator I finished up that section. I still hadn’t decided how I wanted to do the tuning capacitors for this receiver. I really am not in the mood to use 2-80pF variable capacitors. I opted to go with a 0-50 variable cap that you need a screwdriver to tune for the band spread and a 20-107 pF air variable for the regular tuning knob. With that decided and done, laying out the pads for the front end began.

The front end is a pretty simple circuit. A toroid that matches the local oscillator, an on the board capacitor and a couple of trim caps. The tricky part of this stage was making sure everything would fit. The particular variable cap I had chosen was pretty big relative to the remainder of the board.

A picture of the board with all of its hardware and a 9V battery for a size comparison.

The particular day I was working on this the family had a variety of activities planned and I had to stop a couple of times and then start back up. About 5p I had finished everything. I decided to go through and double-check all the solder joints. Then I realized that I had forgotten the 3.5mm jack for a speaker or headphones! OK fixed that. I double checked all the solder joints and all looked well. I installed the ICs. When installing ICs you will need to bend the leads ever so slightly inward so that they fit in the socket. It is easiest to do when they are IN the socket. Lightly press one edge of leads into the socket to bend them ever so slightly inward. Then gently set the IC into the socket from the back and roll it forward.

Feeling very good about my progress and nervous about the next steps. It’s time to apply power. More to come!

I’m a relatively new ham. Got my license, joined a club and I’m having fun! I enjoy CW, pedestrian mobile, backpacking, and I dream of building radios at some point. At present I have a wife and daughters so my building time is limited.